Add a filesystem descriptor library to scheduled_test.

pkg/scheduled_test/lib/src/descriptor/file.dart

+// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+library descriptor.file;
+
+import 'dart:async';
+import 'dart:io' as io;
+import 'dart:utf';
+
+import 'package:path/path.dart' as path;
+
+import '../../descriptor.dart' as descriptor;
+import '../../scheduled_test.dart';
+import '../utils.dart';
+import 'utils.dart';
+
+/// A descriptor describing a single file.
+class File extends descriptor.Entry {
+  /// Whether this descriptor describes a binary file. This is only used when
+  /// displaying error messages.
+  final bool binary;
+
+  /// The contents of the file, in bytes.
+  final List<int> contents;
+
+  /// The contents of the file as a String. Assumes UTF-8 encoding.
+  String get textContents => new String.fromCharCodes(contents);
+
+  File.bytes(Pattern name, List<int> contents)

[Bob Nystrom, 2013/02/22 17:58:21]

bytes -> binary

The rest of the package seems to use "binary" pretty consistently, and I think
new File.binary() reads well.

[nweiz, 2013/02/22 20:57:20]

Done.

+      : this._(name, contents, true);
+
+  File(Pattern name, String contents)
+      : this._(name, encodeUtf8(contents), false);
+
+  File._(Pattern name, this.contents, this.binary)
+      : super(name);
+
+  Future create([String parent]) => schedule(() {
+    if (parent == null) parent = descriptor.defaultRoot;
+    return new io.File(path.join(parent, stringName)).writeAsBytes(contents);
+  }, 'creating file $nameDescription');
+
+  Future validate([String parent]) => schedule(() {
+    if (parent == null) parent = descriptor.defaultRoot;
+    var fullPath = entryMatchingPattern(parent, name);
+    return new io.File(fullPath).readAsBytes()
+        .then((actualContents) {
+      if (orderedIterableEquals(contents, actualContents)) return;
+      if (binary) {
+        throw "File $nameDescription didn't contain the expected binary "
+            "data.";

[Bob Nystrom, 2013/02/22 17:58:21]

If the data is pretty small, it might be nice to show a hex dump. Or, if too
big, maybe a hex dump of the head and tail.

[nweiz, 2013/02/22 20:57:20]

I'll add a TODO.

+      }
+      var description = nameDescription;
+      if (name is! String) {
+        description = "'${path.basename(fullPath)}' (matching $description)";
+      }
+      throw "File $description should contain:\n"
+          "${prefixLines(textContents)}\n"
+          "but actually contained:\n"
+          "${prefixLines(new String.fromCharCodes(actualContents))}";

[Bob Nystrom, 2013/02/22 17:58:21]

Consider stealing the comparison code in test_pub for this. It tries to
highlight which lines are different or missing so it's easier to see where the
difference is.

[nweiz, 2013/02/22 20:57:20]

Done.

+    });
+  }, 'validating file $nameDescription');
+
+  Stream<List<int>> load([String pathToLoad]) {
+    if (pathToLoad != null) {
+      return errorStream("Can't load '$pathToLoad' from within "
+          "$nameDescription: not a directory.");
+    }
+
+    return new Future.immediate(contents).asStream();
+  }
+
+  String describe() {
+    if (name is String) return name;
+    return 'file matching $nameDescription';
+  }
+}